Finding out how to unblock the heads

It’s really worth servicing the heads annually so you know your way around, and making sure you’ve got some spares. Plus, there’s less chance of a blockage caused by years of deposits in the pipe if it gets a regular service.

If it blocks, you realise how important the heads is: it’s as vital a piece of kit as the engine. Some skippers simply carry a new pump and bin the old one, but often the problem is easily solved if you know where to look – and you have a strong stomach.

The joker valve is not at all funny, but it’s the heart of the heads pump

The instruction manual usually has an exploded diagram, but most heads have a pump that both fills and empties the bowl and has several valves to manage the flow in and out. The blockage is usually close to the bowl so begin there. Probe away with the piece of bent wire which every boat should carry, then follow the pipe to the first valve. At this point you need the right tools. Just when you have completely lost your sense of humour, you reach the joker valve.

Take real care to avoid spillages into the bilge or you will regret it for weeks. Disinfectant is essential, not just for hygiene but to kill the smell. Use lots of it. Have a bucket handy – for several reasons. I am rarely affected by seasickness, but I find it almost impossible to unblock the heads at sea without feeling ill.